Short answers, pulled from the story.
Sparta rose to become a major military power around 650 BC and retained that status until 371 BC, when Thebes defeated it at the Battle of Leuctra. During its peak around 500 BC, Sparta had between 20,000 and 35,000 citizens.
The helots were state-owned people descended from Greeks the Spartans had conquered in Messenia and Laconia. They worked the land, retaining half the yield, and could marry and own limited property, but were subject to systematic terror including the Krypteia, a secretive institution that killed helots to keep the population in fear. Each year when Ephors took office, they ritually declared war on the helots.
The agoge was the Spartan military training regimen that began at age seven for male citizens. Boys lived in communal messes, trained in physical combat and weapons, and also studied reading, writing, music, and dancing. They were trained to survive privation and could be admitted as foreign students, a status known as trophimoi.
Spartan women received formal education in music, dance, singing, and poetry, unlike women in any other Greek city-state. They could own and control property, and in later classical Sparta women were the sole owners of at least 35 per cent of all land. Marriage was delayed until a woman's late teens or early twenties, compared to ages twelve or thirteen in Athens.
Gorgo was the wife of king Leonidas I and daughter of king Cleomenes. Herodotus records that as a young girl she advised her father to resist a bribe, and she is credited with decoding a wax-covered wooden tablet that carried a warning about the Persian invasion. Plutarch preserves several sayings attributed to her.
Sparta's defeat at the Battle of Leuctra in 371 BC by Thebes under Epaminondas proved unrecoverable. The loss also freed Messenia from Spartan control, ending the helot labour supply on which the city's agriculture depended. Spartan citizenship had already fallen from around 9,000 to below 1,000 by Aristotle's time, and to roughly 700 at the accession of Agis IV in 244 BC.